Conversion of hydrocarbons



Sept. 2, 1941. c. G. GERHOLD CONVERSION oFHYDROCMBONSv AFiled March 8, 1939 Patented Sept. 2, 1941 Clarence G. Gerhold, Chicago, Ill., assigner toA Universal Oil Products Company, Chicago, lll., a corporation of Delaware Application March 8,1939, Serial N0. 260,494.

3 Claims. Cl. 196-10) The process of this invention relates particularly to the conversion of butenes contained in 4-carbon atom hydrocarbon fractions into normally liquid hydrocarbons boiling within the range of motor fuel by catalyzed polymerization reactions.

The invention is more specically concernedwith the manufacture of octenes of isomerc structure which are utilizable as such as high anti-knock blending material in gasolines inferior in this respect, or hydrogenatable to produce high octane number iso-octanes which are particularly adapted to use in airplane engines.

The manufacture of high octane number'fuels has received considerable impetus from the demands of high compression ratio airplane engines which operate with a hot intake manifold and which employ superchargers 'at high altitudes.

Fuels for this service must be completely re` liable -and not given to depositing gum in the feed lines or carburetors and thus far the best answer to the problem has been the manufacture of mixtures of iso-octanes which have both high anti-knock rating and complete saturation rendering them incapable of forming gums. At the present time, considerable eiort is being exaction forms esters.

hydrocarbon fraction and dissolved polymers whereby sulfuric acid is neutralized, and substantially olefin-free 4-carbon atom hydrocarbons are removed from the polymers in a fractionator; said improvements comprise heating said fractionator by direct steam injection, and

subjecting debutanized polymers to contact with caustic soda solution and steam whereby sulfuric acid esters are hydrolyzed, and thereafter the polymers are subjected to distillation to separate an octene fraction hydrogenatable to isooctane of high octane number.

In the process for producing iso-octenes from mixtures of butenes and butanes by polymerization of the former with sulfuric acid at temperatures substantially above normal atmospheric temperature, a part of the` acid entering. the re- In order to prepare the isooctene fraction for hydrogenation to iso-octane. it is necessary to remove these esters. ily these esters are decomposed by externally applied heat, but this procedure results in the formation of sulfur dioxide and of other sulfur pended to produce these octanes from 4carbon atom hydrocarbons comprising both butenes and butanes present in gas mixtures produced incidental to oil cracking operations. The present invention is a contribution to this type of proc- -A ess.

Among other methods which have been used to polymerize the butenes present in gas fractions obtained from cracked gas mixtures are those employing `mineral acid catalysts under compounds arising from subsequent action of sulfur dioxide on olens. According to the Aimproved process of the present invention all heating of the polymer products is carried :out in intimate contact with water thereby promoting hydrolysis of the esters present and avoiding their decomposition with the resultant liberation of sulfur dioxide which would react-with the polymers to produce contaminating sulfur compounds and .also cause corrosion of the equipment.

These improved results are obtained by eiTecting the necessary heating by direct steam-injection4 j at two points 'in the process iiow.

diierent conditions of operation which have been l found` conducive to the production of octenes.

Sulfuric acid is employed for this purpose in the form of aqueous solutions of different concentrations. The present invention is an improvement in a process for polymerizing butenes in the presence of sulfuric acid as catalyst.

In one specific embodiment the present invention comprises improvements in a process in which a 4-carbon atom hydrocarbon fraction containing isobutene and n-butenes is subjected to contact with sulfuric acid under conditions adequate to eiect inter-polymerization of isobutene and n-butenes, the sulfuric acid is separated from the #l1-carbon atom hydrocarbon fraction containing dissolved polymers, said sulfuric acid is recycled to further contact with incoming 4-carbon atom hydrocarbon fraction, caustic soda solution is added tothe acid treated 4carbon atom 55 From the debutanizer, in which the. butane is separated from the polymer; thev customary reboiler is eliminated and direct steam injection substituted, the condensate from this direct steam injection being withdrawn from the bottom of the debutanizer together with the polymer. Such substitution of direct steam injection for external heating makes it possible to operate the debutanizer at a higher bottom temperature, without thermal decomposition'of esters, so that a second debutanization of the polymers is unnecessary.

Direct'steam injectionisutilized, also, in the hydrolysmgA step of the process in which the debutanized polymers are heated with caustic soda solution for effecting hydrolysis and ren'lova'lv of small amounts of contaminating sulfurlc acid esters. To indicate in a general way the type 0f proc.'

Ordinarers now which characterizes the present invention,theattacheddrawinghasbeenprovided which indicates tically by the use of conventional inter-connected units drawn in side elevation an arrangement of plant apparatus in which operations typical of the process may be carried'out.

Line I, containing valve 2, indicates a charging line for the n of the 4-carbon atom Ihydrocarbon fraction containing isobutene and normal butenes, such as may be obtained as an overhead in the stabilization of a primarily cracked naphtha. Pump 3 is provided in case the charge is not under suilicient pressure to permit the proper iiow through the succeeding equipmentfthough if the gases are available under suillcient pressure, usually inthe approximate order of 150-600 pounds per square inch,

' this pump maybe dispensed with. From pump 3, line l, containing valve i, leads to heat exchanger 6 in which the 4-carbon atom hydrocarbon fraction is warmed, after which it is withdrawn through line 1, containing valve I and is conducted into line l, containing valve It, beyond which the 4-earbon4 -atom hydrocarbon fraction is mixed with Sil-70% sulfuric acid introduced in the following manner: Y

Sulfuric acid of the desired concentration is introduced from an outside source through line Il, containing valve I2, by pump I3 discharging through line Il and valve li, into line I6 and valve Il and thence into line l between valve Il and pump I8. From pump Il the commingied sulfuric acid and 4-carbon atom hydrocarbon fraction are passed through line It, containing valve 20, to cooler 2 l, provided with lines 2|' and 22 for circulation of a cooling medium, and then are conducted through line 22, containing valve 2l, to the inlet line of time-tank 2l. Although only one time-tank 2l is shown in the diagrammatic drawing it is within the scope of this invention to use a plurality of such time-tanks each maintained at a temperature in the approximate range of 1'15-200" F. From the time-tank Y 24, or a plurality of time-tanks, the mixture of hydrocarbons and sulfuric acid may be conducted acid contained in line 25 maybe passed through valves 26 and 32 into line, to be mixed therein with the original hydrocarbon charging stock and recycled by pump I8 to cooler 2l and later to time-tank 2l. If desired, used sulfuric acid may be withdrawn through branch line 3l containing valve 2l.' and conducted to waste or storage. 'Ihe hydrocarbon layer, separating in separator 29 and comprising mainly a solution of butene polymers in butane-butene fraction, is withdrawn through line 33, mntaining valve 3l. and passed into heat exchange relationship with the incoming 4-carbon atom hydrocarbon fraction in heat exchanger 6. already mentioned,`being` then conducted through line l5, containing valve 26. to settling tank Il wherein entrained lsulfuric acid separates and is returned through line Il, containing valve I9; to line it in which it mixes with the incoming fresh sulfuric acid. From the top of settling tank'21' the polymer solution is conducted through line Il, containing valve ll, to line '42 in which it mixes with causticsoda solution introduced from an outside source by way mixer 48, line l! and valve 50 to vaporizer il of line-, containing valve M. by pump 4l discharging through line and valve l1 into line l2. already mentioned. In this line it is commingied with the polymer product dissolved in the acid treated i-carbon atom hydrocarbon fraction. From line 42 themixture of hydrocarbons and caustic soda solution passes through heated conveniently by steam admitted through line 52 and discharging through line 53. From vaporizer 5I the mixture of hydrocarbons and l caustic discharges through line 54, containing valve 55, to debutanizer, 56, which is preferably operated under a pressure of approximately 100 pounds per square inch.

The mixture admitted to debutanizer Si comprises the added caustic soda solution, unconverted butane-butene fraction, butene polymers and small amounts of sulfuric acid esters. In l carbon fraction vaporized in debutanizer i6. is-

released through line 59, containing valve it, passed through cooler 6i and line 62, containing valve 63, to condensate receiver 64, provided with the conventional gas release line S5, containing valve 6i. If desired, the condensate may be released from condensate receiver N through line il, containing valve 68, or it may be withdrawn through line 69 and valve I0 by pump 1I discharging through line 12 containing valve 13 andl thence conducted to storage through line 'l5 containing valve 14, or a part may be recycled through line 16, containing valve 11, to the top of debutanizer 5i to assist in controlling the temperature therein.

. The polymers debutanized in debutanizer 5U and the commingied caustic soda solution are withdrawn through line I8 and valve 19 by pump 2l, and discharged through line 8l and valve l2' -in which they are commingied with steam admittedfrom an outside source through line 89, containing valve !l( The mixture of polymer, caustic, and steam is conducted through line I8 to a time-tank, or a plurality lof time-tanks, indicated as time-tank ll in the attached diagrammatic drawing. This mixture is contacted in time-tank 9| under approximately 250 pounds pressure at temperatures of the order of 20o-300 F. and then is withdrawn through line I2. convalve S3, paed through line Il and valve l5 to separator or it may be passed from line l2 through valves 93 and 91 w line I2, al-

ready mentioned, and then recycled with or without the admission of more steam to time-tank il.

From separator I6 the caustic soda solution diluted by condensate from the injected steam may be withdrawn through line $2, containing valve 9S, and passed through line Ill, containing valve Ill, to the recycling line 83, already mentioned: or this diluted caustic soda solution. or a portion thereoLmay be discharged through line |02, containing valve |03, to line |04 and thence to waste or storage. I

The polymer puriiled by the treatment with caustic solution is released from separator 96 through line |05, containing valve |06, and passed to fractionator |01. Fractinator |01 is normally operated at a slight superatmospheric pressure taining valve ||0, thence through cooler line Y ||2 and valve ||3y to pump H4 discharging through line H5, containing valve H6, and passed through line ||1 to storage.

'I'he overhead vapors from fractionator |01, comprising principally iso-octenes, pass through line ||8, containing valve ||9, thence through cooler and line |2|, containing valve |22, to condensate receiver 23 equipped with la coni'rxsitional gas release line |24, containing valve sate receiver |23 may be withdrawn through line |20 and valve |21 by pump |23 and may be passed through line |29, containing valve |30, to the top of the fractlonator column |01 to assist in controlling the temperatures therein.

-Also the octene withdrawn by pump |23 may be discharged through line |3l, containing valve |32, and passed through line |33-to storage, or this fraction may be withdrawn from condensate receiver |23 vthrough drawoif line |34 containing valve |35. v

The essential features of the present inven- 'Ihe octene fraction contained in condention have been described in suilicient detail to.r

permit the practical operation of the process by those qualied for such work. In the following section an example is introduced to indicate the type of results obtainable in practice.

though with no intent -to unduly limit the broad A scope-of the invention.

Using 69% sulflu'ic acid as catalyst in an apparatus such as that indicated in the attached diagrammatic drawins. afi-carbon atom hydrocarbon fraction containing 16% isobutene, 32%

normal butenes, and 52% butanes was polymerized at F. under 300 pounds pressure. Sixty percent of the butenes so treated were converted into an octane fraction hydrogenat'able to isooctane of 97-99 octane number.

During this run the debutanizer was heated steam into directcontact with and separate said esters'.

to 400 F. by injection of superheated steam without formation of sulfur dioxide by decomposition of sulfuric acid esters dissolved in the polymers. The debutanized polymers were next subjected to hydrolysis in the presence of admixed caustic soda solution with heating by direct injection of steam effecting removal .of the sulfuric acid esters, which if allowed to remain would undergo decomposition during the subsequentfractional distillation liberating sulfur dioxide, whichin turn would react with the polymers producing contaminating sulfur compounds.

'I'he nature of the process of the present invention and its practical application are evident from the preceding specification and illustrated data presented, although neither section is intended to unduly limit-its generally broad scope.

I claim as my invention: 1. In the polymerization of vnormally gaseous lens'in the presence of sulfuric acidat polymerizing temperatures 'above atmospheric whereby there is formed a polymer liquid containing dissolved gases and sulfuric acid esters andthe polymer liquid reboiled to liberate gases therefrom, the method which comprises supplying the heat for said reboiling by direct introduction of steam to said liquid to prevent decomposition of the esters and then treating the liquid with additional steam in the presence of alkali to hydrolyze and separatesaid esters. v

2. In the polymerization of olefins in the olens in the presence of sulfuric acid at polymerizing temperatures above atmospheric whereby there is .formed a polymer liquid containing 4' carbon atom hydrocarbons and sulfuric acid esters, the method which comprises introducing v d liquid to vaporize 4 carbon atom hydrocarb ns therefrom without substantial decomposition of said esters, and then treating the liquid th additional steam, in the presence o f alkali to hydrolyze 'CLARENCE G. GERHOLD. 

